halo.. i face problem when i execute the programming.

it appear the error as :
1.obj : error LNK2001: unresolved external symbol "double __cdecl NR::trapzd(doub le (__cdecl*)(doub le),double,doub le,int)" (?trapzd@NR@@YA NP6ANN@ZNNH@Z)
Debug/1.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.

can anyone help me ? thanks in advance .

below is the programming...